1. Field of Invention
This invention relates generally to apparatus for machining a workpiece to create a shaped article that conforms to a specification therefor, and more particularly to devices for accurately positioning the workpiece in the course of a manufacturing procedure and for accurately positioning the machine tool engaging the workpiece.
2. Description of Related Art
In a typical machine for manufacturing a shaped article that conforms to a predetermined specification, the workpiece or blank to be machined is held on a horizontal table. This table is movable in X and Y directions to position the workpiece relative to the machine tool for shaping it, the tool being movable in the Z direction. Hence, in the course of a machining operation, the tool cuts material from the workpiece as it changes its position.
The present invention is concerned with those articles of manufacture which must be machined in the round to create the desired configuration and therefore requires that the workpiece be rotated as it is being cut. An example of one such article is an eyeglass lens whose simplest shape is a pure circle. But modern eyeglass lenses, particularly those referred to as xe2x80x9cdesignerxe2x80x9d eyeglasses are non-circular and may have relatively complex contours.
In order to machine a blank for a designer lens, the blank must be held on a rotary worktable which is turned with respect to a machine tool that cuts into the periphery of the blank to contour the blank in accordance with the designer""s specification.
In order to precisely conform the configuration of the lens to the designer""s specification, the rotary position of the worktable and the axial position of the machine tool must be precisely coordinated to correctly contour the workpiece. While existing machines for these purposes are capable of accurately positioning the workpiece as well as the tool, they are highly complex and costly, and contribute significantly to the expenses incurred in manufacturing the lenses.
In view of the foregoing the main object of this invention is to provide devices for precisely positioning a workpiece and a machine tool engaging the workpiece so as to manufacture a shaped article that conforms to a specification therefor.
More particularly, an object of this invention is to provide devices of the above type which are driven by a stepping motor that acts through a reciprocating mechanism to precisely position the workpiece and the tool.
A significant advantage of these devices is that they are uncomplicated and less costly than existing devices for the same purpose, thereby reducing the expenses incurred in manufacturing a shaped article.
Briefly stated, these objects are attained in devices adapted to position exactly a workpiece and a machine tool for machining the workpiece to create a shaped article that conforms to a specification therefor. The device associated with the workpiece includes a rotary table in which the workpiece is held so that it can be machined in the round by the tool. The table is turned by a slider that is driven by a stepping motor and is reciprocated by a pair of drums which are linked by flexible metal bands to opposite ends of the slider. Then when the motor causes the drums to rotate clockwise, the slider is pulled in one direction by the bands, and when the drums are caused to rotate counterclockwise, the slider is pulled in a reverse direction. A similar device serves to exactly position the machine tool.